25143 Itokawa

25143 Itokawa

Greyscale (black & white) image of 25143 Itokawa as observed by JAXA's Hayabusa
Discovery
Discovered by LINEAR
Discovery date 26 September 1998
Designations
Named after
 Hideo Itokawa
1998 SF36
Apollo asteroid,
Mars-crosser asteroid
Orbital characteristics
Epoch 18 August 2005 (JD 2453600.5)
Aphelion 1.695 AU (253.520 Gm)
Perihelion 0.953 AU (142.568 Gm)
1.324 AU (198.044 Gm)
Eccentricity 0.280
1.52 a (556.355 d)
25.37 km/s
294.502°
Inclination 1.622°
69.095°
162.760°
Physical characteristics
Dimensions 535 × 294 × 209 m[1]
Mass (3.51±0.105)×1010 kg,[1] (3.58±0.18)×1010 kg[2]
Mean density
 1.9 ±0.13 g/cm³,[1] 1.95 ± 0.14 g/cm³[2]
~0.1 mm/s²
~0.2 m/s
0.5055 d (12.132 h)[3]
Albedo 0.53[4]
Temperature ~206 K
Spectral type
 S
19.2

    25143 Itokawa (/ˌiːtoʊˈkɑːwə/; Japanese: イトカワ [itokawa]) is an Apollo and Mars-crosser asteroid. It was the first asteroid to be the target of a sample return mission, the Japanese space probe Hayabusa, and the smallest asteroid photographed by a spacecraft.

    Discovery and naming

    The asteroid was discovered in 1998 by the LINEAR project and was given the provisional designation 1998 SF36. In August 2003,[5] it was officially named after Hideo Itokawa, a Japanese rocket scientist.

    Description

    Itokawa is an S-type asteroid. Radar imaging by Goldstone in 2001 observed an ellipsoid 630 ± 60 m long and 250 ± 30 m wide.[6][7]

    The Hayabusa mission confirmed these findings and also suggested that Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters and a very rough surface studded with boulders, described by the mission team as a 'rubble pile'.[8] Furthermore, the density of the asteroid is too low for it to be made from solid rock. This would mean that Itokawa is not a monolith but rather a 'rubble pile' formed from fragments that have cohered over time. Based on Yarkovsky–O'Keefe–Radzievskii–Paddack effect measurements, a small section of Itokawa is estimated to have a density of 2.9 g/cm³, whereas a larger section is estimated to have a density of 1.8 g/cm³.[9]

    Itokawa's orbit
    This artist’s impression, based on detailed spacecraft observations, shows the strange peanut-shaped asteroid Itokawa.

    Exploration

    In 2000, it was selected as the target of Japan's Hayabusa mission. The probe arrived in the vicinity of Itokawa on 12 September 2005 and initially "parked" in an asteroid–Sun line at 20 km (12 mi), and later 7 km (4.3 mi), from the asteroid (Itokawa's gravity was too weak to provide an orbit, so the spacecraft adjusted its orbit around the Sun until it matched the asteroid's). Hayabusa landed on 20 November for thirty minutes, but it failed to operate a device designed to collect soil samples. On 25 November, a second landing and sampling sequence was attempted. The sample capsule was returned to Earth and landed at Woomera, South Australia on 13 June 2010, around 13:51 UTC (23:21 local). On 16 November 2010, the Japan Aerospace Exploration Agency reported that dust collected during Hayabusa's voyage was indeed from the asteroid.[10]

    Surface features

    Names of major surface features were proposed by Hayabusa scientists and accepted by the Working Group for Planetary System Nomenclature of the International Astronomical Union. Also, the Hayabusa science team is using working names for smaller surface features.[11][12] The following tables list the names of geological features on the asteroid.[13] No naming conventions have been disclosed for surface features on Itokawa.

    Craters

    Crater Named after
    Catalina Catalina Observatory which performs Catalina Sky Survey
    Fuchinobe Fuchinobe in Sagamihara, Japan
    Gando Gando, Canary Islands
    Hammaguira Hammaguira French Special Weapons Test Centre, Hammaguir
    Kamisunagawa Kamisunagawa, Hokkaidō
    Kamoi Kamoi, Yokohama
    Komaba Komaba in Meguro, Tokyo
    Laurel Laurel, Maryland
    Miyabaru Radar site of the Uchinoura Space Center in Japan.
    San Marco San Marco platform, an old oil platform near Kenya that served as a launch pad for Italian spacecraft.

    Regiones

    Regiones (geologically distinct areas) on Itokawa.

    Regio Named after
    Arcoona Regio Arcoona, Australia
    LINEAR Regio Lincoln Near-Earth Asteroid Research
    MUSES-C Regio MUSES-C, name of the Hayabusa probe prior to launch.
    Ohsumi Regio Ōsumi Peninsula
    Sagamihara Regio Sagamihara, a town in Japan where Institute of Space and Astronautical Science is located.
    Uchinoura Regio Uchinoura, a town in Japan (now part of Kimotsuki), the location of Uchinoura Space Center, Hayabusa launch site.
    Yoshinobu Regio Launch site in the Tanegashima Space Center, Japan.

    Analysis of particles reported in August 2011

    Schematic view of 25143 Itokawa[14]

    The 26 August 2011, issue of Science devoted six articles to findings based on dust that Hayabusa had collected from Itokawa.[15] Scientists' analysis suggested that Itokawa was probably made up from interior fragments of a larger asteroid that broke apart.[16] Dust collected from the asteroid surface is thought to have been exposed there for about eight million years.[15]

    Scientists used varied techniques of chemistry and mineralogy to analyze the dust from Itokawa.[16] Itokawa's composition was found to match the common type of meteorites known as "low-total-iron, low metal ordinary chondrites".[17] Another team of scientists determined that the dark iron color on the surface of Itokawa was the result of abrasion by micrometeoroids and high-speed particles from the Sun which had converted the normally whitish iron oxide coloring.[17]

    See also

    References

    1. 1 2 3 Akira Fujiwara, et al., The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa, Science, Vol. 312. no. 5778, pp. 1330 – 1334, 2 June 2006
    2. 1 2 Shinsuke Abe, et al., Mass and Local Topography Measurements of Itokawa by Hayabusa, Science, Vol. 312. no. 5778, pp. 1344 – 1347, 2 June 2006
    3. ↑ M. Kaasalainen, et al., CCD photometry and model of MUSES-C target (25143) 1998 SF36, Astronomy and Astrophysics, v.405, p.L29-L32 (2003)
    4. ↑ S. M. Lederer, et al., Physical characteristics of Hayabusa target Asteroid 25143 Itokawa, Icarus, v. 173, p. 153–165 (2005)
    5. ↑ "Official Approval of Names on ITOKAWA by IAU". Press Release of JAXA. 3 March 2009.
    6. ↑ Ostro, S. J.; Benner, L. A. M.; Nolan, M. C.; Giorgini, J. D.; Jurgens, R. F.; Rose, R.; Yeomans, D. K. (2001). "Radar Observations of Asteroid 25143 (1998 SF36)". Bulletin of the American Astronomical Society. 33: 1117. Bibcode:2001DPS....33.4113O.
    7. ↑ "Radar Observations of Asteroid 25143 Itokawa (1998 SF36)" (PDF). Archived (PDF) from the original on 8 April 2015. Retrieved 8 April 2015.
    8. ↑ "Hayabusa: Itokawa Beckons as Japan's Spacecraft Searches for Places to Touch Down". Archived from the original on 12 May 2008. Retrieved 11 August 2008.
    9. ↑ "The Anatomy of an Asteroid". ESO. 5 February 2014. Retrieved 5 February 2014.
    10. ↑ Atkinson, Nancy (16 November 2010). "Confirmed: Hayabusa Nabbed Asteroid Particles". Universe Today. Archived from the original on 6 December 2010. Retrieved 16 November 2010.
    11. ↑ "Itowaka Geological Map". Archived from the original on 26 February 2009. Retrieved 11 August 2008.
    12. ↑ "Local site names on Itowaka". Archived from the original on 26 February 2009. Retrieved 11 August 2008.
    13. ↑ USGS: Itokawa nomenclature
    14. ↑ "The Anatomy of an Asteroid". ESO Press Release. Retrieved 6 February 2014.
    15. 1 2 "Asteroid Dust Confirms Meteorite Origins". New York Times. 25 August 2011. Retrieved 26 August 2011.
    16. 1 2 Nakamura, Tomoki; Noguchi, Takaaki; Tanaka, Masahiko; Zolensky, Michael E.; Kimura, Makoto; Tsuchiyama, Akira; Nakato, Aiko; Ogami, Toshihiro; Ishida, Hatsumi; Uesugi, Masayuki; Yada, Toru; Shirai, Kei; Fujimura, Akio; Okazaki, Ryuji; Sandford, Scott A.; Ishibashi, Yukihiro; Abe, Masanao; Okada, Tatsuaki; Ueno, Munetaka; Mukai, Toshifumi; Yoshikawa, Makoto; Kawaguchi, Junichiro (26 August 2011). "Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites". Science. 333 (6046): 1113–6. Bibcode:2011Sci...333.1113N. doi:10.1126/science.1207758. PMID 21868667. Retrieved 26 August 2011.
    17. 1 2 "Most Earth meteorites linked to single asteroid". Los Angeles Times. 26 August 2011. Retrieved 26 August 2011.

    Further reading

    External links

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